I'm growing several different Panicums, both P.virgatum and P.amarum, and a few cultivars of P.v. including 'strictum.' I have them in pots and in the ground, in exposures ranging from full sun to part (3-4 hours) sun. Without exception, those in full sun are doing better than those in part sun.

So, I guess it depends on your definition of "partial shade." I'm 2 zones warmer, so our sun exposure is different.

As far as water is concerned, once they are established, Panicum is fairly drought resistant. That would be after a full season of well-watered growth. Still, they need to be watered every week or two in the absence of rain.